Prior Art
Straight bar knitting machines have had, since the inception of the Cotton's Patent machines in the 1860's (see British patent specification Nos. 3123 of 1864) the same overall configuration with only small variations. In the most common multi-section straight bar machines of the Cotton's Patent type a composite movement is imparted to the needle bar by upper levers pivotably fastened to each end of the needle bar to support the needle bar and provide an up-down motion therefor and by an upright support arm conjointly pivotable with the needle bar to provide an in-out swinging motion. The motions are produced from cams on a single rotatable cam shaft which cams engage levers secured to longitudinally extending shafts mounting the up-down levers or an in-out lever which operated a lower link connected to the aforesaid support arm. From the side the levers, support arms and links have the appearance of a quadrangle with the longitudinal shafts at one upper corner, the needle bar outside the quadrangle at another upper corner and the cams below the quadrangle. When seen from the front the levers, support arms and links are spaced apart by mounting them at different parts of the longitudinal shafts so that one cam could serve a number of levers. Actuating mechanisms for catch bars and knockover bars and any other mechanisms added in the course of time were mounted on the machine using similar longitudinally extending shafts (see for example U.S. Pat. No. 3,397,555).
In a less commonly used single section straight bar knitting machine (see British patent specification Nos. 411,517 and 867,391) the basic needle bar actuation mechanism was not altered. Longitudinal shafts were grouped more closely together and certain parts of added rib-knitting mechanisms were actuated by separate cams one at each side of the single section.
The Pourchot British patent specification No. 643,624 shows a common longitudinally extending shaft for the levers and the single cam shaft located inside the aforesaid quadrangular arrangement, but does not provide an adequate pressing of the needle beards or hooks (to close them prior to knockover) because the needle bar is pulled into press by a spring, and the needle bar projects upward of the quadrangular arrangement so detracting from constructional rigidity.
The long path through which force was transmitted from the cams, to a lever, to a longitudinal shaft and then through lever and optionally links and support arms to the needle bar restricted the directness of needle bar actuation, its rigidity and its ability to operate at speed. Similar actuation arrangements for the other motions provided the same type of difficulty. The floor area occupied was generally considerable.
To combine the various actuation components it was generally necessary to make them of different shape, length or size so that the value of components stocked for producing the straight bar machines and for maintaining them was high.
These factors (the difficulty of incorporating additional components and the manufacturing cost) combined so that the machines had only a limited potential for further development, be it development for increasing production speed or for performing additional functions or performing more flexibly.
Furthermore the knitting head on known machines itself it not well arranged for compactness or high speed operation. Slurcock noise and jackwear increase sharply at higher speeds and the knockover bar, which is squeezed between the needle bar and sinker bar, tends to bend at high speed or require considerable reinforcement to resist bending.
Even if a high speed operation were possible, the cam drive mechanism would cause the followers to jump off the cam at cam peaks so destroying the accurate control over the different motions.
The draw mechanism generally employs rigid rods friction boxes and slur bars which occupy considerable space and do not lend themselves to high speed operation. Endless band mechanisms developed as an alternative lead to breakage and occupy space at the rear of the knitting head.
It is the object of this invention firstly to provide a novel straight bar machine configuration which avoids or mitigates the restrictions inherent in the known Cotton's Patent type machine and has development potential. It is another object to provide a machine including a suitably arranged knitting head capable of high knitting speeds. It is another object to provide a compact machine which can be operated at high speed and/or make effective use of floor space. It is another object of the invention to provide a knitting machine using standardised actuation mechanisms for the different components.